Tensile and Flexural Strength Properties of Surface-modified Banana Fibre Epoxy Composites

Abstract

There is presently a rise in the research and development of composites reinforced using natural fibres because of an increase in environmental awareness driven by climate change concerns. This is because natural fibres are abundant, eco-friendly, cost effective and low in density. Additionally, they also have a high strength to weight ratio compared to synthetic and mineral fibres e.g. asbestos, Kevlar, and asbestos. Since natural fibres are low in density, they enable the production of composites with good mechanical properties and low mass per unit volume. Fibrous plants like bananas are abundant in tropical countries and are used as agricultural food crops. At the moment, banana fibres are a waste product and the only cost would be in its collection, grading and treating. Therefore, the fibres can be used for industrial applications such as making roofing tiles, furniture, seat cushions, interior panels of automobiles, and marine equipment (fishing nets and boats). Despite there being numerous research published on the strengthening effect of different banana fibre surface modification methods, there are no known studies that have been carried out to compare alkalization and oxidative treatment of Giant Cavendish banana fibres. This study represents the first species specific study that focused on examining and comparing the strength properties of untreated and surface-modified Giant Cavendish banana fibres. The banana fibres were mercerized using 0.06M Sodium Hydroxide (NaOH) and treated using 0.003M Potassium Permanganate (KMnO4) solutions and the fibres’ strength properties determined. The untreated and surface-modified fibres, in uniaxial alignment and varying volume fractions, were then used as reinforcement in a general purpose epoxy (glycidyl amine) resin matrix. Tensile and Flexural tests were then performed on the composites. 0.003M KMnO4 treated banana fibres had the highest mean tensile strength of 209.32 MNm-2, which translated to a 65.92% gain in tensile strength while the 0.06M NaOH treated vi (mercerized) banana fibres had a mean tensile strength of 162.23 MNm-2, which was a 28.60% gain in tensile strength compared to the untreated fibres respectively. The 0.003M KMnO4 treated banana fibre-reinforced epoxy resin recorded the greatest gain in tensile strength with a maximum tensile strength value of 7.42 MNm-2 at a fibre volume fraction of 5.40%. This in turn translated to a 470.77% gain in tensile strength compared to the unreinforced specimen. 0.06M NaOH treated banana fibre-reinforced epoxy resin on the other hand, recorded a maximum tensile strength value of 7.07 MNm-2 at an optimal fibre volume fraction of 5.50%. This translated to a 443.85% gain in tensile strength compared to the unreinforced epoxy specimens. The untreated banana fibre-reinforced epoxy resin had a maximum tensile strength value of 5.10 MNm-2 at an optimal fibre volume fraction of 3.30% compared to the unreinforced epoxy specimens. Similarly, 0.003M KMnO4 surface-modified banana fibre-reinforced epoxy resin recorded the greatest gain in flexural strength with a maximum modulus of rupture (MOR) of 14.15MNm-2 at a fibre volume fraction of 2.90%. This translated to a 256.42% increase in flexural strength compared to the unreinforced epoxy resin specimens. 0.06M NaOH treated banana fibre-reinforced epoxy resin had a maximum MOR of 9.83 MNm-2 at a fibre volume fraction of 2.80%. This in turn, translated to a 147.61% gain in flexural strength compared to the unreinforced specimens. Untreated banana fibre reinforced epoxy resin had a maximum MOR value of 5.26 MNm-2 at a fibre volume fraction of 2%. This was a 32.49% gain in flexural strength compared to the neat epoxy specimens. These results were in agreement with the findings reported by Zin et al. [1] which showed that improved interfacial bond strength between surface-modified lignocellulosic fibres and polymeric matrices results in composites with better strength properties.